In my 30+ years, most of what I have learned really boils down to two big things:
1: LIFE IS COMPRISED OF A SERIES OF MOMENTS
Some are big. Some are small. Some are good. Some are not. Some are predictable and some seem to come out of nowhere. Moments in life are diverse and widespread, but they all have one thing in common;
MOMENTS ARE FLEETING
2: Life is work and it's worth working hard, but there is little point of all that effort if you can't take the time to enjoy it and be happy. So do that. Take the time to enjoy life and be happy.